1. Field of the Invention
The present invention relates to a solid-state image sensing device applied to a CMOS image sensor for use in, e.g., a cellphone with an image sensor, a digital camera, or a video camera.
2. Description of the Related Art
The conventional methods of increasing the dynamic range of a CMOS image sensor are proposed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2001-189893 (Patent Publication 1 hereinafter) and Jpn. Pat. Appln. KOKAI Publication No. 2000-23044 (Patent Publication 2 hereinafter). The method of Patent Publication 1 is applied to an incomplete transfer type photodiode and may produce afterimages or white defects, so the image quality is difficult to improve. By contrast, the method of Patent Publication 2 corresponds to a complete transfer type, so neither afterimages nor white defects form unlike in Patent Publication 1. However, since the dynamic range is increased by using a detector, the leak from this detector may produce dark nonuniformity or KTC noise and degrade the image quality by factors different from those in Patent Publication 1. In addition, both the methods add a long-storage-time signal and short-storage-time signal and output the sum. This makes it difficult to separate the long-storage-time signal and short-storage-time signal.